Endoplasmic reticulum localization signals

ABSTRACT

The invention relates to cellular localization signals. In particular, the invention relates to endoplasmic reticulum localization signals in monomeric or multimeric form. The localization signals are utilized as research tools or are linked to therapeutics. Disclosed are methods of making and using polypeptides and modified polypeptides as signals to localize therapeutics, experimental compounds, peptides, proteins and/or other macromolecules to the endoplasmic reticulum of eukaryotic cells. The polypeptides of the invention optionally include linkage to reporters, epitopes and/or other experimental or therapeutic molecules. The invention also encompasses polynucleotides encoding the localization signals and vectors comprising these polynucleotides.

This application claims benefit of priority to provisional application60/826,517, filed 21 Sep. 2006.

FIELD OF INVENTION

The invention relates to subcellular localization signals. Inparticular, the invention relates to endoplasmic reticulum localizationsignals in monomeric or multimeric form. The multimers may behomomultimers or heteromultimers. The monomers and multimers areutilized as research tools or are linked to therapeutics.

This application has subject matter related to application Ser. No.10/724,532 (U.S. Pat. No. 7,071,295), Ser. No. 10/682,764(US2004/0185556, PCT/US2004/013517, WO2005/040336), Ser. No. 11/233,246,and US20040572011P (WO2005116231). Each of these patents andapplications is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

Drugs that act intracellularly generally enter cells by diffusion. Mostdrugs are small molecules because they have the ability to diffuseacross plasma membranes or organelle membranes to reach their site ofaction. To increase the bioavailability of a drug, often small moleculesmust be modified and/or formulated for greater solubility and/orpermeability, depending on route of administration. Even smalldiffusible drugs may not be efficacious at their site of action. Forexample, multidrug resistance (MDR) may be present, which results inactive efflux of drugs that enter cells with MDR. MDR often occurs incancer cells.

In contrast to small molecules, high molecular weight compounds andpolymer drugs, such as polynucleotides, polypeptides, and othermacromolecules have little to no ability to diffuse across membranes.High molecular weight material is generally internalized by endocytosis.The addition of affinity binding partners to high molecular weightmaterial can direct the high molecular weight compound to specificcells, and thereby result in increased selective uptake. However, onceendocytosed, the material still remains separated from the cellularcytoplasm by a biological membrane.

Endocytosed material is often delivered to the lysosome, where materialsensitive to lysosomal enzymes is quickly degraded if steps are nottaken to protect its breakdown or to facilitate escape from thelysosome. Delivery of high molecular weight compounds to their site ofaction at effective levels is a problem. It is therefore desirable toimprove delivery to a desired subcellular compartment.

One of the first cellular trafficking signals identified was theendoplasmic reticulum (ER) retention signal, KDEL, which preventssecretion of proteins routed to the endoplasmic reticulum. When thissignal is expressed toward the carboxy terminus in proteins that arenormally secreted, these proteins are retained in the endoplasmicreticulum and not secreted (Munro and Pelham, Cell 1987, 48:899-907).

Endogenous and exogenous proteins have varying targeting domains withintheir primary sequence. Such proteins include those described inAndersson, et al. 1999 J Biol Chem 274:15080-4, Cocquerel, et al. 1999 JVirol 73:2641-9, Fons, et al. 2003 J Cell Biol 160:529-39, Gabathuler,et al. 1990 J Cell Biol 111:1803-10, Honsho, et al. 1998 J Biol Chem273:20860-6, Ma, et al. 2002 J Biol Chem 277:27328-36, Mitoma, et al.1992 Embo J 11:4197-203, Mziaut, et al. 1999 J Biol Chem 274:14122-9,Parker, et al. 2004 J Biol Chem 279:23797-805, Pottekat, et al. 2004 JBiol Chem 279:15743-51, Ren, et al. 2003 J Biol Chem 278:52700-9,Szczesna-Skorupa, et al. 2001 J Biol Chem 276:45009-14, Vainauskas, etal. 2005 J Biol Chem 280:16402-9, Watanabe, et al. 1996 J Biol Chem271:26868-75, Zarei, et al. 2004 Proc Natl Acad Sci USA 101:10072-7, andZarei, et al. 2001 J Biol Chem 276:16232-9.

An aspect of the invention is to provide novel monomeric and novelmultimeric endoplasmic reticulum localization signals by modifying oneor more proteins that naturally locate to the endoplasmic reticulum bytruncation or by amino acid substitution. Truncations, amino acidsubstitutions, and other modifications of known ER-locating proteins aremade to minimize endogenous biological activities other thanlocalization. In general, the invention relates to cellular localizationsignals. More specifically, the invention relates to endoplasmicreticulum localization signals in monomeric or multimeric form. Themultimers may be homomultimers or heteromultimers. Multimers are made toexploit cooperation and synergism among individual signals in order tocreate a chimeric localization signal with a strength and/or performancegreater than the constituent individual parts. The monomers andmultimers are utilized as research tools or are linked to therapeutics.Disclosed are methods of making and using polypeptides and modifiedpolypeptides as signals to localize therapeutics, experimentalcompounds, peptides, proteins and/or other macromolecules to theendoplasmic reticulum and contiguous structures of eukaryotic cells. Thepolypeptides of the invention optionally include linkage to reporters,epitopes and/or other experimental or therapeutic molecules. Theinvention also encompasses polynucleotides encoding the localizationsignals and vectors comprising these polynucleotides.

DETAILED DESCRIPTION OF POLYPEPTIDE AND POLYNUCLEOTIDE SEQUENCES

SEQ ID NOS:1-16 are example endoplasmic reticulum localization signalsand polynucleotides encoding them.

Specifically, the polypeptide of SEQ ID NO:1 is encoded by SEQ IDNOS:2-6, wherein the codons of SEQ ID NOS:3-6 have been optimized forvector insertion. SEQ ID NO:4 and SEQ ID NO:6 include flankingrestriction sites. SEQ ID NO:5 and SEQ ID NO:6 differ from SEQ ID NO:3and SEQ ID NO:4, respectively, in that an internal EcoRI restriction hasbeen removed. SEQ ID NO:1 is an embodiment of a multimeric ERlocalization signal of the structure A-S1-B-S2-B-S3-C, wherein A is SEQID NO:42, B is SEQ ID NO:72, and C is SEQ ID NO:75, and wherein S1 is atwo amino acid spacer with the sequence EF, S2 is a four amino acidspacer with the sequence, PGAG, and S3 is a three amino acid spacer withthe sequence, AAA. A multimeric localization signal of structureA-S1-B-S2-B-S3-C is also called herein a heteromultimer (see FIG. 4D).

SEQ ID NO:7 is an embodiment of a multimer of the structureX-S1-Y-S2-Y-S3, wherein X is SEQ ID NO:60, Y is SEQ ID NO:72, S1 is aseven amino acid spacer with the sequence EFGGGGG, S2 is a four aminoacid spacer with the sequence PGAG, and S3 is a five amino acid spacerwith the sequence AAPAA. The polypeptide of SEQ ID NO:7 is encoded bySEQ ID NOS:8-12, wherein the the codons of SEQ ID NOS:9-12 have beenoptimized for vector insertion. SEQ ID NO:10 and SEQ ID NO:12 includeflanking restriction sites. SEQ ID NO:9 and SEQ ID NO:10 differ from SEQID NO:11 and SEQ ID NO:12, respectively, in that an internal EcoRIrestriction has been removed. A multimer of structure X-S1-Y-S2-Y-S3 isalso called herein a heteromultimer (see FIG. 4E). A vector map of avector containing SEQ ID NO:7 is shown in FIG. 11 (labeled LocalizationSignal). SEQ ID NO:7 was expressed in Cos7 cells as shown in FIG. 12.

SEQ ID NO:13 is an embodiment of a multimer of the structureX-S1-Y-S2-Y, wherein X is SEQ ID NO:60, Y is SEQ ID NO:72, S1 is a sevenamino acid spacer with the sequence EFGGGGG, and S2 is a four amino acidspacer with the sequence PGAG. The polypeptide of SEQ ID NO:13 isencoded by SEQ ID NO:14, SEQ ID NO:15 and by SEQ ID NO:16, wherein thecodons of SEQ ID NO:15 and SEQ ID NO:16 have been optimized for vectorinsertion. SEQ ID NO:16 includes flanking restriction sites. A multimerof structure X-S1-Y-S2-Y is also called herein a heteromultimer (seeFIG. 4B).

SEQ ID NOS:17-38 are full length sequences of proteins that localize tothe endoplasmic reticulum. These sequences have the following publicdatabase accession numbers: NP_(—)001007236, Q9Y2B2, CAA77776, AAQ19305,AAF81759, P00180, Q969N2, NP_(—)071581, NP_(—)003479, CAI20063, Q7M370,CAA23446, AAS89356, BAA19247, B34759, AAB97308, AAP35497, NP_(—)999425,NP_(—)999113, XP_(—)343784.

SEQ ID NOS:39-69 represent examples of monomeric endoplasmic reticulumlocalization signals. SEQ ID NOS:39-69 are subsequences of SEQ IDNOS:17-38, which represent examples of peptide sequences that conferendoplasmic reticulum routing and/or retention.

SEQ ID NOS:70-77 represent examples of monomeric endoplasmic reticulumretention signals.

DETAILED DESCRIPTION OF DRAWINGS

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the Office upon request and paymentof the necessary fee.

FIGS. 1A-1D show examples of homomultimeric localization signals withoutspacers.

FIGS. 2A-2C show examples of homomultimeric localization signals withspacers.

FIGS. 3A-3E show examples of heteromultimeric localization signalswithout spacers.

FIGS. 4A-4E show examples of heteromultimeric localization signals withspacers.

FIGS. 5A-5H show examples of localization signals linked to an epitopetag.

FIGS. 6A-6H show examples of localization signals linked to a reporter.

FIGS. 7A-7H show examples of localization signals linked to anexperimental or therapeutic polypeptide.

FIGS. 8A-8H show examples of localization signals linked to an epitopetag, and an experimental or therapeutic polypeptide.

FIGS. 9A-9H show examples of gene constructs where localization signalsare linked to an experimental or therapeutic polypeptide, with anoptional epitope tag and/or reporter.

FIGS. 10A-10D show examples of vectors containing endoplasmic reticulumlocalization signal gene constructs.

FIG. 11 shows a diagram of the vector used to transform the Cos7 cellsof FIG. 12. Abbreviations are as follows: Neo stands for neomycinresistance gene; Amp stands for ampicillin resistance gene; ori standsfor origin of replication; P stands for promoter domain; E stands forexpression domain; 3 stands for 3′ regulatory domain.

FIG. 12 shows activity of the endoplasmic reticulum localization signalof SEQ ID NO:7. Cos7 cells were transfected with DNA from the vectorshown in FIG. 11. The green color identifies the location of antibodieswhich recognize the c-Myc epitope linked to chloramphenicolacetyltransferase fragment and the localization signal. The red coloridentifies the ER resident protein calreticulin. This image is aco-localization image, wherein yellow areas represent colocalization ofred and green, and demonstrate the targeting of a polypeptide ofinterest (chloramphenicol acetyltransferase fragment) to the endoplasmicreticulum using the localization signal of SEQ ID NO:7.

FIGS. 13 and 14 show activity of the endoplasmic reticulum localizationsignal of SEQ ID NO:1. COS7 African green monkey kidney cells wereplated at 4,000 cells per square centimeter in a 24 well glass bottomplate (MatTek Cat. No. P24G-1.0-13-F) coated with poly-D-Lysine. Thecells were grown in DMEM with 10% Fetal bovine serum at 37° C. for 24hours. Plasmid DNA (0.4 ug) was introduced using CaPO4 (Invitrogen CaPO4transfection kit), according to the manufacturer's protocol. After 24hours, cells were washed twice with Ca2+/Mg2+-free PBS. The cells werefixed in ice-cold methanol (−20 C) for 5 minutes. Cells were then washedtwice with PBS and incubated in a blocking solution of 8% bovine serumalbumin (BSA) in PBS for 30 minutes. Primary antibody (mouse anti-FLAGM2 antibody from SigmaAldrich) was added at 2 μg/ml in a solution of PBSwith 3% bovine serum albumin (BSA). After 2 h, the antibody was removedand the wells were rinsed 5×5 minutes with PBS. The last rinse wasreplaced with Goat anti-mouse secondary antibody conjugated toAlexaFluor 546 fluorescent dye. The antibody concentration was 200 ng/mland was diluted in PBS with 3% BSA. After 45 minutes at room temperatureand in the dark, the antibody was removed. Cells were rinsed three timesin PBS, then incubated with 300 ng/mL DAPI containing PBS for 5 minutes.The cells were covered with Vectashield Mounting Medium (VectorLaboratories) before imaging.

The pictures in FIGS. 13 (vectorID-VVN8159) and 14 (vectorID-VVN8174)were generated using a Zeiss Axio-observer microscope fitted with anapotome structured light device and represent a magnification of 630× ofa 500 nm slice through each group of cells. Pictures were taken with aset of red filters to visualize Alexa546 (excitation maximum 546nm/emission maximum 608 nm) or blue filters (excitation maximum 365nm/emission maximum 445 nm) to visualize the DAPI nuclear stain. Thepunctuate and reticular patterns are indicative of ER staining, as isthe exclusion of stain from the nucleus.

FIG. 15 shows a diagram of the vector used to transform the Cos7 cellsof FIG. 13. Plasmid DNA vectors have the following architecture: VVN8159contains a transgene with these components 5′ to 3′: PROMOTER(EF1alpha)-POLYPEPTIDE OF INTEREST (ERK1 decoy)-EPITOPE TAG (FLAG)-SEQID NO:1 (LOCALIZATION SIGNAL)-SV40PolyA. Abbreviations are as follows:Neo stands for neomycin resistance gene; Amp stands for ampicillinresistance gene; on stands for origin of replication; P stands forpromoter domain; T stands for transcription domain; 3 stands for 3′regulatory domain.

FIG. 16 shows a diagram of the vector used to transform the Cos7 cellsof FIG. 14. Plasmid DNA vectors have the following architecture: VVN8174contains a transgene with these components 5′ to 3′: PROMOTER(EF1alpha)-POLYPEPTIDE OF INTEREST (ERK1 decoy)-EPITOPE TAG (modifiedFLAG)-SEQ ID NO:1 (LOCALIZATION SIGNAL)-SV40PolyA. Abbreviations are asfollows: Neo stands for neomycin resistance gene; Amp stands forampicillin resistance gene; on stands for origin of replication; Pstands for promoter domain; T stands for transcription domain; 3 standsfor 3′ regulatory domain.

BRIEF DESCRIPTION OF THE INVENTION

The invention relates to monomeric or multimeric endoplasmic reticulumlocalization signals. Various embodiments of the endoplasmic reticulumlocalization signals are represented in SEQ ID NOS:1-77. Morespecifically, the invention relates to monomeric or multimericlocalization signals that comprise any one or more of SEQ ID NOS:39-77.Additionally, the invention relates to monomeric or multimericpolypeptide localization signals comprising one or more subsequences ofSEQ ID NOS:17-38 or any portion thereof. Furthermore, the inventionrelates to monomeric or multimeric polypeptide localization signals withat least about 80%, 85%, 90%, 95%, 96%, 97%, 98% and 99% sequenceidentity to a polypeptide comprising one or more of SEQ ID NOS:39-77 orany portion thereof. Furthermore, the invention relates to monomeric ormultimeric polypeptide localization signals with at least about 80%,85%, 90%, 95%, 96%, 97%, 98% and 99% sequence identity to a polypeptidecomprising one or more subsequences of SEQ ID NOS:17-38.

Multimeric endoplasmic reticulum localization signals, which can behomomultimers or heteromultimers, are chimeric polypeptides composed oftwo or more monomers. An example of a monomeric localization signal isthe polypeptide represented by SEQ ID NO:39. SEQ ID NO:39 is a selectedsubsequence of wild type full length SEQ ID NO:17. An example of ahomomultimer is a polypeptide comprising a dimer or multimer of SEQ IDNO:39. An example of a heteromultimer is a polypeptide comprising SEQ IDNO:39 and one or more of SEQ ID NOS:40-77. There are numerous ways tocombine SEQ ID NOS:39-77 into homomultimeric or heteromultimericlocalization signals. Furthermore, there are numerous ways to combineadditional subsequences of SEQ ID NOS:17-38 with each other and with SEQID NOS:39-77 to make multimeric localization signals.

The localization signals of the invention optionally comprise spaceramino acids before, after or between monomers. SEQ ID NO:13 is anexample of a heteromultimer with the structure X-S1-Y-S2-Y, where X andY are selected from SEQ ID NOS:39-77 and S1 and S2 are amino acidspacers. This invention intends to capture all combinations ofhomomultimers and heteromultimers without limitation to the examplesgiven above or below. In this description, use of the term localizationsignal encompasses monomeric, homomultimeric, and/or heteromultimericpolypeptide localization signals.

A monomeric ER localization signal is a polypeptide where at least aportion of the polypeptide is capable of functioning as an endoplasmicreticulum (ER) routing signal and/or as an endoplasmic reticulumretention signal. An ER routing signal functions to direct a polypeptideto the ER, while a retention signal functions to retain the polypeptidein the ER or to prevent secretion of ER-localized polypeptides.

A multimeric localization signal comprises two or more monomericlocalization signals.

A homomultimeric localization signal is a multimer where each of themonomers is identical in amino acid sequence.

A heteromultimeric localization signal is a multimer where some of themonomers are not identical in amino acid sequence.

One embodiment of the invention is a monomeric localization signalcontaining a polypeptide at least 80% identical to one of SEQ IDNOS:39-69.

Another embodiment of the invention is a heteromultimeric localizationsignal containing polypeptides at least 80% identical to two or more ofSEQ ID NOS:39-69.

Another embodiment of the invention is a heteromultimeric localizationsignal containing two or more of SEQ ID NOS:70-77.

Another embodiment of the invention is a heteromultimeric localizationsignal containing polypeptides at least 80% identical to two or more ofSEQ ID NOS:39-77.

Another embodiment of the invention is a heteromultimeric localizationsignal containing a polypeptide at least 80% identical to one or more ofSEQ ID NOS:39-69 adjacent to one or more of SEQ ID NOS:70-77.

Another embodiment of the invention is a heteromultimeric localizationsignal containing a polypeptide at least 80% identical to one or moresubsequences of SEQ ID NOS:17-38 adjacent to one or more of SEQ IDNOS:70-77.

Another embodiment of the invention is a heteromultimeric localizationsignal containing polypeptides at least 80% identical to two or moresubsequences of SEQ ID NOS:17-38.

The localization signals of the invention are optionally linked toadditional molecules or amino acids that provide an epitope, a reporter,and/or an experimental or therapeutic molecule. The epitope and/orreporter and/or experimental molecule and/or therapeutic molecule may bethe same molecule. The epitope and/or reporter and/or experimentalmolecule and/or therapeutic molecule may also be different molecules.Experimental or therapeutic molecules include but are not limited toproteins and polypeptides. In one embodiment, a localization signal fortethering a protein or macromolecule of interest to the cyoplasmic faceof the ER is made where the localization signal is placed toward theC-terminus of the resultant fusion protein (FIGS. 7A, 7C, 7E, 7H). Inanother embodiment, a localization signal for tethering a protein ormacromolecule of interest to the cyoplasmic face of the ER is made wherethe localization signal is placed toward the N-terminus of the resultantfusion protein (FIGS. 7B, 7D, 7F, 7G).

The invention also encompasses polynucleotides comprising nucleotidesequences encoding endoplasmic reticulum localization signals. Thenucleic acids of the invention are optionally linked to additionalnucleotide sequences encoding polypeptides with additional features,such as an epitope, a reporter, an experimental and/or therapeuticmolecule. The polynucleotides are optionally flanked by nucleotidesequences comprising restriction endonuclease sites and othernucleotides needed for restriction endonuclease activity. The flankingsequences optionally provide unique cloning sites within a vector andoptionally provide directionality of subsequence cloning. Further, thenucleic acids of the invention are optionally incorporated into vectorpolynucleotides. The localization signals of this invention have utilityin compositions for research tools and/or therapeutics.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to endoplasmic reticulum localizationsignals. Various embodiments of the localization signals are representedby SEQ ID NOS:1-77. Multimeric localization signals are chimericpolypeptides comprising two or more monomeric localization signals. Anexample of a monomeric localization signal is the polypeptiderepresented by SEQ ID NO:39. SEQ ID NO:39 is a selected subsequence ofwild type full length SEQ ID NO:17. Another example of a monomericlocalization signal is the polypeptide represented by SEQ ID NO:68. Eachof SEQ ID NOS:39-77 represents an individual localization signal inmonomeric form. SEQ ID NOS:39-69 are selected examples of subsequencesof SEQ ID NOS:17-38, however, other subsequences of SEQ ID NOS:17-38 mayalso be utilized as monomeric localization signals. Monomericsubsequences of SEQ ID NOS:17-38 may be wild type subsequences.Additionally, monomeric subsequences of SEQ ID NOS:17-38 may have someamino acids different than the wild type parent. Furthermore, monomericlocalization signals may have 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%sequence identity to a polypeptide comprising one or more of SEQ IDNOS:39-77. Furthermore, monomeric localization signals may have 80%,85%, 90%, 95%, 96%, 97%, 98% and 99% sequence identity to a subsequenceof SEQ ID NOS:17-38.

An example of a homomultimeric localization signal is a polypeptidecomprising a dimer or multimer of SEQ ID NO:49. An example of aheteromultimeric localization signal is a polypeptide comprising SEQ IDNO:39 and one or more of SEQ ID NOS:40-77. There are numerous ways tocombine SEQ ID NOS:39-77 into homomultimeric or heteromultimericlocalization signals. Furthermore, there are numerous ways to combineadditional subsequences of SEQ ID NOS:17-38 with each other and with SEQID NOS:39-77 to make multimeric localization signals.

Multimeric localization signals may comprise any two or more of SEQ IDNOS:39-77. A dimer or multimer of SEQ ID NO:66 is an example of ahomomultimer. An example of a heteromultimer is a polypeptide comprisingSEQ ID NO:77 and one or more of SEQ ID NOS:39-76. Another example of aheteromultimer is a polypeptide comprising SEQ ID NO:70 and one or moreof SEQ ID NOS:39-69. Another example of a heteromultimer is apolypeptide comprising SEQ ID NO:72 and one or more of SEQ ID NOS:39-71.There are numerous ways to combine SEQ ID NOS:39-77 into homomultimericor heteromultimeric localization signals. SEQ ID NOS:39-69 are selectedexamples of subsequences of SEQ ID NOS:17-38, however, additionalsubsequences, wild type or mutated, may be utilized to form multimericlocalization signals. The instant invention is directed to all possiblecombinations of homomultimeric and heteromultimeric localization signalswithout limitation.

SEQ ID NOS:17-38 represent full length sequences of proteins that haveendoplasmic reticulum localization activity. SEQ ID NOS:39-69 aresubsequences of SEQ ID NOS:17-38 that are capable of conferringendoplasmic reticulum localization. SEQ ID NOS:70-77 are amino acidsequences that confer endoplasmic reticulum retention. Polypeptidesubsequences that are identical to their wild type parent may be used aspart of a localization signal, however in one embodiment some aminoacids are mutated to another amino acid, such as one of the naturallyoccurring amino acids including, alanine, aspartate, asparagine,cysteine, glutamate, glutamine, phenylalanine, glycine, histidine,isoleucine, leucine, lysine, methionine, proline, arginine, valine,tryptophan, serine, threonine, or tyrosine. Mutation of amino acids maybe performed for various reasons including, but not limited to,minimization of undesired biological activity, introduction or removalof secondary structure in the polypeptide; disruption of protein/proteininteraction; modification of charge, hydrophobicity, or stability of thepolypeptide; and introduction or removal of restriction sites in thenucleic acid encoding the polypeptide. As shown by SEQ ID NO:7, FIG. 12and Example 4 below, the localization signals of the invention arecapable of directing polypeptides of interest to the endoplasmicreticulum of eukaryotic cells.

In general, endoplasmic reticulum localization signals are built byidentifying proteins that localize to the endoplasmic reticulum.Sometimes it is desirable to utilize wild type truncations as buildingblocks. However, it is sometimes desirable to modify one or more aminoacids to enhance the localization. Other reasons for modifying the wildtype sequences are to remove undesired characteristics, such asenzymatic activity or modulation of an endogenous cellular function.Monomeric building blocks may include an endoplasmic reticulumlocalization sequence as well as amino acids adjacent and contiguous oneither side. Monomeric building blocks may therefore be any lengthprovided the monomer confers endoplasmic localization, routing and/orretention. For example, the monomer may comprise at least 1, 2, 3, 4, 5,6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24,25, 26, 27, 28, 29, 30-100 or more amino acids adjacent to theendoplasmic reticulum localization, routing or retention-conferringsequence.

For example, in one embodiment, the invention comprises an endoplasmicreticulum localization signal comprising at least one copy of a peptideselected from the group consisting of:

a) a peptide at least 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% identicalto a peptide comprising amino acid residues corresponding to amino acidresidues 2338-2428 of the amino acid sequence of SEQ ID NO:17;

b) a peptide at least 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% identicalto a peptide comprising amino acid residues corresponding to amino acidresidues 2341-2425 of the amino acid sequence of SEQ ID NO:17;

c) a peptide at least 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% identicalto a peptide comprising amino acid residues corresponding to amino acidresidues 2349-2417 of the amino acid sequence of SEQ ID NO:17; and

d) a peptide at least 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% identicalto a peptide comprising amino acid residues corresponding to amino acidresidues 2359-2407 of the amino acid sequence of SEQ ID NO:17.

In another embodiment, the invention comprises an endoplasmic reticulumlocalization signal comprising at least one copy of a peptide selectedfrom SEQ ID NOS:70-77 and comprising at least one copy of a peptideselected from the group consisting of:

a) a peptide at least 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% identicalto a peptide comprising amino acid residues corresponding to amino acidresidues 2338-2428 of the amino acid sequence of SEQ ID NO:17;

b) a peptide at least 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% identicalto a peptide comprising amino acid residues corresponding to amino acidresidues 2341-2425 of the amino acid sequence of SEQ ID NO:17;

c) a peptide at least 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% identicalto a peptide comprising amino acid residues corresponding to amino acidresidues 2349-2417 of the amino acid sequence of SEQ ID NO:17; and

d) a peptide at least 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% identicalto a peptide comprising amino acid residues corresponding to amino acidresidues 2359-2407 of the amino acid sequence of SEQ ID NO:17.

As used herein, the terms “correspond(s) to” and “corresponding to,” asthey relate to sequence alignment, are intended to mean enumeratedpositions within a reference protein, e.g., IP3 Receptor (SEQ ID NO:17),and those positions that align with the positions on the referenceprotein. Thus, when the amino acid sequence of a subject peptide isaligned with the amino acid sequence of a reference peptide, e.g., SEQID NO:17, the amino acids in the subject peptide sequence that“correspond to” certain enumerated positions of the reference peptidesequence are those that align with these positions of the referencepeptide sequence, but are not necessarily in these exact numericalpositions of the reference sequence. Methods for aligning sequences fordetermining corresponding amino acids between sequences are describedbelow.

Additional embodiments of the invention include monomers based on anyputative or real polypeptide or protein that has endoplasmic reticulumlocalization, routing or retention activity, such as those identified bySEQ ID NOS:39-77. Furthermore, if the protein has more than onelocalization subsequence, then more than one monomer may be identifiedtherein.

Another embodiment of the invention is a nucleic acid moleculecomprising a polynucleotide sequence encoding at least one copy of alocalization signal polypeptide.

Another embodiment of the invention is a nucleic acid molecule whereinthe polynucleotide sequence encodes one or more copies of one or morelocalization signal polypeptides.

Another embodiment of the invention is a nucleic acid molecule whereinthe polynucleotide sequence encodes at least a number of copies of thepeptide selected from the group consisting of 2, 3, 4, 5, 6, 7, 8, 9 or10.

Another embodiment of the invention is a vector comprising a nucleicacid molecule encoding at least one copy of an endoplasmic reticulumlocalization signal.

Another embodiment of the invention is a recombinant host cellcomprising a vector comprising a nucleic acid molecule encoding at leastone copy of an endoplasmic reticulum localization signal.

Another embodiment of the invention is a method of localizing apolypeptide to an endoplasmic reticulum subcellular compartment in acell comprising linking a polypeptide open reading frame to alocalization signal open reading frame to create a fusion protein codingsequence, and transfecting the fusion protein coding sequence into ahost cell and culturing the transfected host cell under conditionssuitable to produce at least one copy of the fusion protein.

Another embodiment of the invention is a method of delivering atherapeutic molecule to a subcellular location in a cell comprisingtransfecting a vector comprising a nucleic acid molecule encoding atleast one copy of a localization signal linked to a therapeutic moleculeinto a host cell and culturing the transfected host cell underconditions suitable to produce at least one copy of the localizationsignal-containing therapeutic molecule.

The invention also relates to modified localization signals that are atleast about 80%, 85%, 90% 95%, 96%, 97%, 98% or 99% identical to areference polypeptide. A modified localization signal is used to mean apeptide that can be created by addition, deletion or substitution of oneor more amino acids in the primary structure (amino acid sequence) of alocalization signal protein or polypeptide. The terms “protein” and“polypeptide” and “peptide” are used interchangeably herein. Thereference polypeptide is considered to be the wild type protein or aportion thereof. Thus, the reference polypeptide may be a protein whosesequence was previously modified over a wild type protein. The referencepolypeptide may or may not be the wild type protein from a particularorganism.

A polypeptide having an amino acid sequence at least, for example, about95% identical to a reference an amino acid sequence is understood tomean that the amino acid sequence of the polypeptide is identical to thereference sequence except that the amino acid sequence may include up toabout five modifications per each 100 amino acids of the reference aminoacid sequence encoding the reference peptide. In other words, to obtaina peptide having an amino acid sequence at least about 95% identical toa reference amino acid sequence, up to about 5% of the amino acidresidues of the reference sequence may be deleted or substituted withanother amino acid or a number of amino acids up to about 5% of thetotal amino acids in the reference sequence may be inserted into thereference sequence. These modifications of the reference sequence mayoccur at the N-terminus or C-terminus positions of the reference aminoacid sequence or anywhere between those terminal positions, interspersedeither individually among amino acids in the reference sequence or inone or more contiguous groups within the reference sequence.

As used herein, “identity” is a measure of the identity of nucleotidesequences or amino acid sequences compared to a reference nucleotide oramino acid sequence. In general, the sequences are aligned so that thehighest order match is obtained. “Identity” per se has an art-recognizedmeaning and can be calculated using published techniques. (See, e.g.,Computational Molecular Biology, Lesk, A. M., ed., Oxford UniversityPress, New York (1988); Biocomputing: Informatics And Genome Projects,Smith, D. W., ed., Academic Press, New York (1993); Computer Analysis ofSequence Data, Part I, Griffin, A. M., and Griffin, H. G., eds., HumanaPress, New Jersey (1994); von Heinje, G., Sequence Analysis In MolecularBiology, Academic Press (1987); and Sequence Analysis Primer, Gribskov,M. and Devereux, J., eds., M Stockton Press, New York (1991)). Whilethere exist several methods to measure identity between twopolynucleotide or polypeptide sequences, the term “identity” is wellknown to skilled artisans (Carillo, H. & Lipton, D., Siam J Applied Math48:1073 (1988)). Methods commonly employed to determine identity orsimilarity between two sequences include, but are not limited to, thosedisclosed in Guide to Huge Computers, Martin J. Bishop, ed., AcademicPress, San Diego (1994) and Carillo, H. & Lipton, D., Siam J AppliedMath 48:1073 (1988). Computer programs may also contain methods andalgorithms that calculate identity and similarity. Examples of computerprogram methods to determine identity and similarity between twosequences include, but are not limited to, GCG program package(Devereux, J., et al., Nucleic Acids Research 12(i):387 (1984)), BLASTP,ExPASy, BLASTN, FASTA (Atschul, S. F., et al., J Molec Biol 215:403(1990)) and FASTDB. Examples of methods to determine identity andsimilarity are discussed in Michaels, G. and Garian, R., CurrentProtocols in Protein Science, Vol 1, John Wiley & Sons, Inc. (2000),which is incorporated by reference. In one embodiment of the presentinvention, the algorithm used to determine identity between two or morepolypeptides is BLASTP.

In another embodiment of the present invention, the algorithm used todetermine identity between two or more polypeptides is FASTDB, which isbased upon the algorithm of Brutlag et al. (Comp. App. Biosci. 6:237-245(1990), incorporated by reference). In a FASTDB sequence alignment, thequery and subject sequences are amino sequences. The result of sequencealignment is in percent identity. Parameters that may be used in aFASTDB alignment of amino acid sequences to calculate percent identityinclude, but are not limited to: Matrix=PAM, k-tuple=2, MismatchPenalty=1, Joining Penalty=20, Randomization Group Length=0, CutoffScore=1, Gap Penalty=5, Gap Size Penalty 0.05, Window Size=500 or thelength of the subject amino sequence, whichever is shorter.

If the subject sequence is shorter or longer than the query sequencebecause of N-terminus or C-terminus additions or deletions, not becauseof internal additions or deletions, a manual correction can be made,because the FASTDB program does not account for N-terminus andC-terminus truncations or additions of the subject sequence whencalculating percent identity. For subject sequences truncated at the N-and C-terminal ends, relative to the query sequence, the percentidentity is corrected by calculating the number of bases of the querysequence that are N- and C-terminus to the reference sequence that arenot matched/aligned, as a percent of the total bases of the querysequence. The results of the FASTDB sequence alignment determinematching/alignment. The alignment percentage is then subtracted from thepercent identity, calculated by the above FASTDB program using thespecified parameters, to arrive at a final percent identity score. Thiscorrected score can be used for the purposes of determining howalignments “correspond” to each other, as well as percentage identity.Residues of the query (subject) sequences or the reference sequence thatextend past the N- or C-termini of the reference or subject sequence,respectively, may be considered for the purposes of manually adjustingthe percent identity score. That is, residues that are notmatched/aligned with the N- or C-termini of the comparison sequence maybe counted when manually adjusting the percent identity score oralignment numbering.

For example, a 90 amino acid residue subject sequence is aligned with a100 residue reference sequence to determine percent identity. Thedeletion occurs at the N-terminus of the subject sequence and therefore,the FASTDB alignment does not show a match/alignment of the first 10residues at the N-terminus. The 10 unpaired residues represent 10% ofthe sequence (number of residues at the N- and C-termini notmatched/total number of residues in the query sequence) so 10% issubtracted from the percent identity score calculated by the FASTDBprogram. If the remaining 90 residues were perfectly matched the finalpercent identity would be 90%. In another example, a 90 residue subjectsequence is compared with a 100 reference sequence. This time thedeletions are internal deletions so there are no residues at the N- orC-termini of the subject sequence which are not matched/aligned with thequery. In this case the percent identity calculated by FASTDB is notmanually corrected.

The multimeric localization signals of the invention optionally comprisespacer amino acids before, after, or between monomers (for example,FIGS. 2A-2C, 4A-4E). Additionally, the localization signals of theinvention optionally comprise spacer amino acids before or after thelocalization signal (for example, FIGS. 2C, 4E, 5A, 5B, 5E, 5F, 6A, 6B,6E, 6F, 7C, 7D, 7E, 7G, 8C, 8D, 8E, 8G and 8H). The length andcomposition of the spacer may vary. An example of a spacer is glycine,alanine, polyglycine, or polyalanine. In addition to providing spacebetween monomers, spacers can be used for the purpose of engineeringrestriction sites in the encoding nucleic acid and can be used formodifying secondary structure of the polypeptide encoded. Specificexamples of spacers used between monomers in SEQ ID NO:7 are thepeptides EFGGGGG and PGAG. In the instance of SEQ ID NO:7, theproline-containing spacer is intended to break an alpha helicalsecondary structure. At the C-terminal end of SEQ ID NO:7 is a fiveamino acid spacer with the sequence AAPAA. This particular spacerprovides a linker to another module coding region such as a reporter,epitope or experimental or therapeutic polypeptide. The spacer aminoacids may be any amino acid and are not limited to alanine, glycine andproline. The instant invention is directed to all combinations ofhomomultimers and heteromultimers, with or without spacers, and withoutlimitation to the examples given above or below.

The localization signals of the invention are optionally linked toadditional molecules or amino acids that provide an epitope, a reporter,and/or an experimental or therapeutic molecule (FIGS. 5A-5H, 6A-6H,7A-7H, 8A-8H). Non-limiting examples of epitope are FLAG™ (Kodak;Rochester, N.Y.), HA (hemagluttinin), c-Myc and His6. Non-limitingexamples of reporters are alkaline phosphatase, galactosidase,peroxidase, luciferase and fluorescent proteins. Non-limiting examplesof experimental proteins are enzymes, enzyme binding partners,signalling factors, structural factors, and peptide ligands, metabolicbinding factors, nucleic acid binding factors, and cellular bindingfactors. The epitopes, reporters and experimental or therapeuticmolecules are given by way of example and without limitation. Theepitope, reporter, experimental molecule and/or therapeutic molecule maybe the same molecule. The epitope, reporter, experimental moleculeand/or therapeutic molecule may also be different molecules.

Localization signals and optional amino acids linked thereto can besynthesized chemically or recombinantly using techniques known in theart. Chemical synthesis techniques include but are not limited topeptide synthesis which is often performed using an automated peptidesynthesizer. Peptides can also be synthesized utilizing non-automatedpeptide synthesis methods known in the art. Recombinant techniquesinclude insertion of localization signal encoding nucleic acids intoexpression vectors, wherein nucleic acid expression products aresynthesized using cellular factors and processes.

Linkage of an epitope, reporter, experimental or therapeutic molecule toa localization signal can include covalent or enzymatic linkage. Whenthe localization signal comprises material other than a polypeptide,such as a lipid or carbohydrate, a chemical reaction to link moleculesmay be utilized. Additionally, non-standard amino acids and amino acidsmodified with lipids, carbohydrates, phosphate or other molecules may beused as precursors to peptide synthesis. The localization signals of theinvention have utility as therapeutic targeting molecules. Pure peptidesrepresent embodiments of conventional peptide therapeutics. However,polypeptides or proteins linked to localization signals have utility assubcellular tools or therapeutics. For example, polypeptides depictedgenerically in FIGS. 7A-7H represent localization signals with utilityas subcellular tools or therapeutics. Localization signal-containinggene constructs are also delivered via gene therapy. FIGS. 10B and 10Cdepict embodiments of gene therapy vectors for delivering andcontrolling polypeptide expression in vivo. Polynucleotide sequenceslinked to the gene construct in FIGS. 10B and 10C include genomeintegration domains to facilitate integration of the transgene into aviral genome and/or host genome.

FIG. 10A shows a vector containing an endoplasmic reticulum localizationsignal and fluorescent protein gene construct, wherein the geneconstruct is releasable from the vector as a unit useful for generatingtransgenic animals. For example, the gene construct, or transgene, isreleased from the vector backbone by restriction endonuclease digestion.The released transgene is then injected into pronuclei of fertilizedmouse eggs; or the transgene is used to transform embryonic stem cells.The vector containing a localization signal and reporter gene constructof FIG. 10A is also useful for transient transfection of the transgene,wherein the promoter and codons of the transgene are optimized for thehost organism. The vector containing a gene construct of FIG. 10A isalso useful for recombinant expression of polypeptides in fermentableorganisms adaptable for small or large scale production, wherein thepromoter and codons of the transgene are optimized for the fermentationhost organism.

FIG. 10D shows a vector containing an endoplasmic reticulum localizationsignal gene construct useful for generating stable cell lines.

The invention also encompasses polynucleotides comprising nucleotidesequences encoding monomeric localization signals and multimericlocalization signals. The polynucleotides of the invention areoptionally linked to additional nucleotide sequences encoding epitopes,reporters and/or experimental or therapeutic molecules. Further, thenucleic acids of the invention are optionally incorporated into vectorpolynucleotides. The polynucleotides are optionally flanked bynucleotide sequences comprising restriction endonuclease sites and othernucleotides needed for restriction endonuclease activity. The flankingsequences optionally provide cloning sites within a vector. Therestriction sites can include, but are not limited to, any of thecommonly used sites in most commercially available cloning vectors.Non-limiting examples of such sites are those recognized by NsiI, ApaLI,MfeI, KpnI, BamHI, ClaI, EcoRI, EcoRV, SpeI, AfIII, NdeI, NheI, XbaI,XhoI, SphI, NaeI, SexAI, HindIII, HpaI, and PstI restrictionendonucleases. Sites for cleavage by other restriction enzymes,including homing endonucleases, are also used for this purpose. Thepolynucleotide flanking sequences also optionally provide directionalityof subsequence cloning. It is preferred that 5′ and 3′ restrictionendonuclease sites differ from each other so that double-stranded DNAcan be directionally cloned into corresponding complementary sites of acloning vector.

Localization signals with or without epitopes, reporters, orexperimental or therapeutic proteins are alternatively synthesized byrecombinant techniques. Polynucleotide expression constructs are madecontaining desired components and inserted into an expression vector.The expression vector is then transfected into cells and the polypeptideproducts are expressed and isolated. Localization signals made accordingto recombinant DNA techniques have utility as research tools and/orsubcellular therapeutic delivery agents.

The following is an example of how polynucleotides encoding localizationsignals are produced. Complimentary oligonucleotides encoding thelocalization signals and flanking sequences are synthesized andannealed. The resulting double-stranded DNA molecule is inserted into acloning vector using techniques known in the art. When the localizationsignals are placed in-frame adjacent to sequences within a transgenicgene construct that is translated into a protein product, they form partof a fusion protein when expressed in cells or transgenic animals.

Another embodiment of the invention relates to selective control oftransgene expression in a desired cell or organism. The promoter portionof the recombinant gene can be a constitutive promoter, anon-constitutive promoter, a tissue-specific promoter (constitutive ornon-constitutive) or a selectively controlled promoter. Differentselectively controlled promoters are controlled by different mechanisms.For example, a tetracycline-inducible promoter is activated to express adownstream coding sequence when the cell containing the promoter andother necessary cellular factors is treated with tetracycline. Whentetracycline is removed, gene expression is subsequently reduced. Otherinducible promoters are activated by other drugs or factors. RheoSwitch®is an inducible promoter system available from New England Biolabs(Ipswich, Mass.). Temperature sensitive promoters can also be used toincrease or decrease gene expression. An embodiment of the inventioncomprises a localization signal containing gene construct whoseexpression is controlled by an inducible promoter. In one embodiment,the inducible promoter is tetracycline inducible.

Monomeric and multimeric ER localization signals and methods of makingthese localization signals are disclosed. Below are examples of methodsof using ER localization signals. In general, localization signalslinked to epitopes, reporters, and other desired proteins or moleculesare delivered via adenovirus, lentivirus, adeno-associated virus, orother viral constructs that express protein product in a cell.

Methods

Cellular localization is tested using one or more of the followingtechniques.

Fluorescence microscopy is employed to determine spatial cellularlocalization. Fluorescence microscopy involves autofluorescence offluorescent proteins fused to localization signals of the invention.Alternatively, fluorescence microscopy involves immunofluorescence ofantibodies directed against epitopes fused to localization signals.Anti-epitope antibodies are either directly linked to a fluorochrome orare used in combination with a fluorescent secondary antibody.

Known cellular structures and locations are comparatively illustratedwith well known and/or commercially available stains, dyes, antibodiesand/or other reagents that identify cellular locations. Such reagentsinclude but are not limited to: DAPI, Hoechst stains, acridine orange,Lysotracker (Invitrogen, Carlsbad, Calif.), ERtracker (Invitrogen,Carlsbad, Calif.), Golgitracker (Invitrogen, Carlsbad, Calif.),Mitotracker (Invitrogen, Carlsbad, Calif.), anti-CD25, anti-myc,anti-OSBP, anti-NSF, anti-transferrin receptor, anti-T-cell transferrinreceptor, anti-AP2 alpha subunit, anti-clathrin heavy chain, anti-lamin,anti-histone, anti-histone deacetylase, anti-p53, phalloidin-coumarin,phalloidin-FITC, phalloidin-phycoerythrin, anti-oxysterol bindingprotein, anti-nem sensitive factor, anti-gm130, anti-lamp1, anti-lamp2,acridine orange nonyl bromide, anti-tac antigen, anti-Na/K-ATPase, andanti-EGF receptor (antibody producing hybridomas available from ATCC).

Electron microscopy is employed to determine location at highermagnifications. Slides of cells expressing localization signals fused toepitopes are prepared using techniques known in the art. Anti-epitopeantibodies are either directly linked to a gold label or in combinationwith a gold-labeled secondary antibody.

Immunoblotting is employed to determine quantitative expression levelsand/or to biochemically corroborate microscopic observations.Immunoblotting or western blotting is performed on whole cell lysatesand/or on cells that have been fractionated by density gradientcentrifugation. Antibodies useful for fraction identification by westernblot include but are not limited to anti-lamin, anti-histone,anti-histone deacetylase, anti-p53, anti-oxysterol binding protein,anti-nem sensitive factor, anti-gm130, anti-lamp1, anti-lamp2, anti-tacantigen, anti-caveolin-1 and anti-EGF receptor.

Epitopes for use in localization signal fusion proteins includehemagglutinin (HA), FLAG and Myc, among others. Specifically,localization signals fused to an epitope are expressed in Hela, HCT116,HT1080, HCN1a, HCN2, SHSY5Y, ARPE19-HPV16 p5, U87-MG, C2Bbe1, HEK293,COS1, COS7, MDCK, C2C12, Sol8, P19, 10T1/2 and NIH3T3 (available fromthe ATCC). Anti-hemagluttinin antibodies and fluorescent secondaryantibody are then employed to visualize location using standard methodssuch as those described in Giepmans et al. 2006 Science 312:217-24,incorporated by reference herein. For electron microscopy, methods suchas those described in Ukimura et al. 1997 Am J Pathol. 150:2061-2074(incorporated by reference herein) are employed.

Alternatively, localization signals fused to a fluorescent protein areexpressed in Hela, HCT116, HT1080, HCN1a, HCN2, SHSY5Y, ARPE19-HPV16 p5,U87-MG, C2Bbe1, HEK293, COS1, COS7, MDCK, C2C12, Sol8, P19, 10T1/2 andNIH3T3 (available from the ATCC). Location is visualized using standardmethods such as those described in Giepmans et al. 2006 Science312:217-24, incorporated by reference herein.

For immunoblot analysis, cellular fractions are obtained by taking cellsexpressing localization signals fused to a hemagluttinin epitope, andlightly homogenizing them, for example, in a Dounce homogenizer.Homogenized cells are then subjected to density gradient centrifugationas is known in the art and described in Current Methods in Cell Biology(Volume 1, Chapter 3, pages 3.0.1-3.11.22, Bonafacino et al. editors)(incorporated by reference herein). Fractions from the density gradientcentrifugation are then electrophoresed on an acrylamide gel andsubsequently transferred to a membrane electrophoretically. The membraneis then probed with appropriate anti-hemagluttinin antibodies and/orantibodies to known proteins. By comparing the gel lanes showing ananti-hemagglutinin signal to gel lanes showing antibody signals of knownproteins, cellular location of a localization signal of the invention isdetermined biochemically.

EXAMPLES Example 1

A polypeptide comprising a multimeric endoplasmic reticulum localizationsignal and an epitope is synthesized. The structure of such apolypeptide is generically represented by FIG. 5C. The polypeptide issynthesized on an automated peptide synthesizer or is recombinantlyexpressed and purified. Purified polypeptide is solubilized in media andadded to cells. Verification is performed by visualization of antibodybinding to the epitope.

Example 2

A transgene is constructed using a human cytomegalovirus (CMV) promoterto direct expression of a fusion protein comprising SEQ ID NO:64, SEQ IDNO:69, and SEQ ID NO:72 (LOCALIZATION SIGNAL) and green fluorescentprotein (REPORTER). Such a transgene is generically represented by FIG.9G. The transgene is transfected into cells for transient expression.Verification of expression and location is performed by visualization ofthe fluorescent protein by confocal microscopy.

Example 3

A transgene construct is built to produce a protein product withexpression driven by a tissue-specific promoter. The transgene comprisesa synthetic gene expression unit engineered to encode three domains.Each of these three domains is synthesized as a pair of complimentarypolynucleotides that are annealed in solution, ligated and inserted intoa vector. Starting at the amino-terminus, the three domains in theexpression unit are nucleotide sequences that encode a kinase inhibitor,a FLAG epitope, and an endoplasmic reticulum localization signal. Thelocalization signal is a monomeric, homomultimeric, or heteromultimericlocalization signal as described herein. Nucleotide sequences encoding aFLAG epitope are placed downstream of nucleotide sequences encoding thekinase inhibitor. Finally, nucleotide sequences encoding thelocalization signal are placed downstream of those encoding the FLAGepitope. The assembled gene expression unit is subsequently subclonedinto an expression vector, such as that shown in FIG. 10A, and used totransiently transfect cells. Verification is performed by microscopicvisualization of the epitope immunoreactivity at the endoplasmicreticulum.

Example 4

Subcellularly localized chloramphenicol acetyltransferase fragment wasdemonstrated in the endoplasmic reticulum of Cos7 cells using atransgene construct containing an endoplasmic reticulum localizationsignal, a c-Myc eptitope, and a chloramphenicol acetyltransferasefragment (non-enzymatic) was made. The expression unit containsnucleotides that encode an endoplasmic reticulum localization signal SEQID NO:7 (LOCALIZATION SIGNAL), a c-Myc epitope (EPITOPE), and a fragmentof chloramphenicol acetyltransferase (POLYPEPTIDE OF INTEREST). Thisexpression unit is subsequently subcloned into a vector between a CMVpromoter and an SV40 polyadenylation signal (FIG. 11). The completedtransgene-containing expression vector was then used to transfect Cos7cells. FIG. 12 illustrates the subcellular collocation (yellow) of thec-Myc epitope (green) with calreticulin (red). In the presence of thelocalization signal, chloramphenicol acetyltransferase fragment islocated at the endoplasmic reticulum.

Additionally, subcellularly localized polypeptide of interest wasdemonstrated in the endoplasmic reticulum of Cos7 cells using atransgene construct containing an endoplasmic reticulum localizationsignal, a FLAG (or modified FLAG) eptitope, and an ERK decoy polypeptideof interest. The expression unit of the transgene contains nucleotidesthat encode an ERK decoy (POLYPEPTIDE OF INTEREST), a FLAG (or modifiedFLAG) tag (EPITOPE), and endoplasmic reticulum localization signal SEQID NO:1 (LOCALIZATION SIGNAL). This expression unit was subsequentlysubcloned into a vector between an EF1alpha promoter and an SV40polyadenylation signal (FIG. 15, FIG. 16). The completedtransgene-containing expression vector was then used to transfect Cos7cells. FIGS. 13 and 14 illustrate the subcellular location (red) of theFLAG (or modified FLAG) epitope.

Example 5

Fluorescent protein localization is demonstrated in vivo by making atransgene construct used to generate mice expressing a fusion proteintargeted to the endoplasmic reticulum. The transgene construct is showngenerically in FIG. 10B. The expression unit contains nucleotides thatencode a dimer of SEQ ID NO:49 (LOCALIZATION SIGNAL) and greenfluorescent protein (POLYPEPTIDE). This expression unit is subsequentlysubcloned into a vector between nucleotide sequences including amammalian promoter and an SV40 polyadenylation signal. The completedtransgene is then injected into pronuclei of fertilized mouse oocytes.The resultant pups are screened for the presence of the transgene byPCR. Transgenic founder mice are bred with wild-type mice. Heterozygoustransgenic animals from at least the third generation are used for thefollowing tests, with their non-transgenic littermates serving ascontrols.

Test 1: Southern blotting analysis is performed to determine the copynumber. Southern blots are hybridized with a radio-labeled probegenerated from a fragment of the transgene. The probe detects bandscontaining DNA from transgenic mice, but does not detect bandscontaining DNA from non-transgenic mice. Intensities of the transgenicmice bands are measured and compared with the transgene plasmid controlbands to estimate copy number. This demonstrates that mice in Example 4harbor the transgene in their genomes.

Test 2: Tissues are prepared for microscopic analysis. This experimentdemonstrates the transgene is expressed in tissues of transgenic micebecause green fluorescent protein is visualized in transgenic tissuesbut not in non-transgenic tissues.

These examples demonstrate delivery of molecules to a localized regionof a cell for therapeutic or experimental purposes. The purifiedpolypeptide localization signals linked to therapeutics can beformulated for oral or parenteral administration, topicaladministration, or in tablet, capsule, or liquid form, intranasal orinhaled aerosol, subcutaneous, intramuscular, intraperitoneal, or otherinjection; intravenous instillation; or any other routes ofadministration. Furthermore, the nucleotide sequences encoding thelocalization signals permit incorporation into a vector designed todeliver and express a gene product in a subcellular compartment. Suchvectors include plasmids, cosmids, artificial chromosomes, and modifiedviruses. Delivery to eukaryotic cells can be accomplished in vivo or exvivo. Ex vivo delivery methods include isolation of the intendedrecipient's cells or donor cells and delivery of the vector to thosecells, followed by treatment of the recipient with the cells. Theinvention encompasses transgenes comprising localization signals andnon-human transgenic organisms harboring these transgenes. Thetransgenes may be under the control of inducible promoters ortissue-specific promoters.

Disclosed are endoplasmic localization signals and methods of making andusing these localization signals. The localization signals aresynthesized chemically or recombinantly and are utilized as researchtools or as therapeutic delivery agents. The invention includes linkingmolecules to cellular localization signals for subcellular therapeutics.

What is claimed is:
 1. An isolated polypeptide localization signalcomprising two amino acid sequences at least 90% identical to SEQ ID NO:49.
 2. A polynucleotide encoding the polypeptide of claim
 1. 3. Anexpression vector comprising the polynucleotide of claim
 2. 4. Anisolated host cell comprising the expression vector of claim
 3. 5. Amethod of localizing a polypeptide of interest to an endoplasmicreticulum compartment in a cell, said method comprising: (a) linking thepolynucleotide of claim 2 to a second polynucleotide encoding apolypeptide open reading frame to create a fusion protein codingsequence, and (b) introducing the linked polynucleotide into a host cellunder conditions suitable to produce the fusion protein.